FIG. 1 shows a generic description of a broadband network for providing telephone, internet and TV/video services to subscribers in a number of locations. A series of service providers provide the various services (SP1, SP2, SP3) to the network 10 via conventional access points 12. The network 10 provides connects these to subscribers via routers 14 located close to the subscribers. These can include business locations that can include routers in commercial property 16, and domestic subscribers with routers located in a central office 18 for a neighbourhood of separate dwellings (houses 17), or in a single building 19 such as an apartment building.
Operation of the network is controlled by a control and provisioning system 20 that configures the various elements of the network to operate in the desired manner.
For the function of the control and provisioning system 20, the network can be considered in an abstract way as comprising a core 22 having one or more cells 24, each cell having one or more network elements 26 as is shown in FIG. 2. Subscribers 28 connect to the network elements 26. This structure is not to be confused with the physical elements making up the network. The functional blocks 22, 24, 26 may be wholly or partly resident in the same or different physical elements, depending on the exact size and makeup of the network in question, although typically, each network element 26 will comprise a router.
The operator manages the network function by use of the control and provisioning system 20 which has the functions of establishing the function of each network element 26 and establishing and managing user function and operation. The primary control is effected at the level of the core 22 which defines the topology and configuration of the network, including configuring physical or logical links, assigning IP addresses and making particular service available to users connecting to the network. In an existing system, the data for configuration of the network is held in a core database accessed via an application program interface (API). On start-up, the network module contains no configuration data. As and when required, for example on connection of a new device to the network module, the network module interrogates the database and caches the necessary configuration data locally where it remains until changed. When a change is made to the network configuration, the change is made to the database and an alert sent out over the network to the network modules, which in turn interrogate the database to find the changed information which is then loaded into a corresponding database in the network module where the changed data is cached (the network module database has the same basic structure as the core database but is only populated with data required to configure that network module and its associated network elements).
Since failure of part of the control and provisioning system 20 can cause failure of the whole system to provide the services to the subscribers, the use of backup or secondary systems has been proposed such that on failure of the primary system, operation is transferred to the backup so that service provision can be maintained while the problem with the primary system is addressed. Once the problem with the primary system is solved, operation is handed back from the secondary system to the primary system which then continues to operate until another problem arises. Such an approach is common in network systems.
Both the primary and secondary system include databases that are continually modified during operation. Problems can occur if changes occur in the database of an active system that are not communicated to the other system when it becomes active.